It has previously been proposed to reduce the distortion, and particularly phase distortion, when receiving FM signals in vehicular radios by utilizing two antennae and providing a switch-over device in the receiver which recognizes reflections occurring in the signals received by one of the antennae and, if such recognition is positive, switching over reception to the other antenna. Such a system is described in German Patent Disclosure Document DE-OS 25 14 181, SYKES. Problems which arise in the reception of FM signals in automobile radios which occur when using a single antenna are intended to be avoided by switching over from one antenna to another if the received signals are subject to spurious paths or involve multi-path reception or included reflected or "ghost" signals. The receiving system as described in the aforementioned publication has two antennae, positioned at different locations on the vehicle. The receiver includes a switch-over device which is connected to the radio frequency (RF) preamplifier stage of the radio. The switch-over device is energized in dependence on the respective amplitude of the output signal from the intermediate frequency (IF) amplifier of the automobile radio in such a manner that only that one of the antennae is used which has the best incoming signal. The two respectively different receiving antennae have different directional reception characteristics. This is a necessary requirement for trouble-free operation of such system, since the simultaneous occurrence of reflections of the signals at both the antennae is highly unlikely.
The system as described operates well when the reflection paths are short. In certain locations, such as in built-up urban areas, in mountainous regions and the like, where multi-reflected paths of signals occur frequently, the arrangement as described still does not provide essentially distortion-free reception.